The word "haboob" comes from the Arabic word habb, meaning “wind.” A haboob is a wall of dust as a result of a microburst or downburst. The air forced downward is pushed forward by the front of a thunderstorm cell, dragging dust and debris with it, as it travels across the terrain.

Haboobs occur mostly during the summer months in Phoenix, but are not restricted to the monsoon period. These dust storms are much more serious than dust devils. The wind during a haboob is usually up to about 30 mph and dust can rise high into the air as it blows over the Valley. A haboob can last for up to three hours.

Phoenix experiences various degrees of dust storms, but the haboob is the largest and most dangerous. According to the National Weather Service, Phoenix experiences on average about 3 haboobs per year during the months of June through September.

June 1, 2001
Earlier this year, an unusually large dust cloud that originated in northwest China drifted across the continental United States and lingered over Denver and other areas, at times obscuring views of the Rocky Mountains.

NASA Photographs Huge Clouds of Pollution Over Earth More Stories Featuring Satellite Images @ Eye in the Sky Ancient Fertile Crescent Almost Gone, Satellite Images Show It isn't the first time a giant dust cloud from east Asia has reached the United States. But concerned observers say the vast sweep and the density of this latest one suggests that northwest China's once-fruitful agricultural land is eroding at an alarming rate, becoming useless desert.

China has mounted various efforts to halt the increasing desertification, which is caused by overuse of the land for farming and grazing. Nonetheless, as much as 900 square miles (2,300 square kilometers) of farmland in northern China—an area more than twice the size of Hong Kong—is blown away by the wind each year, according to a Chinese scientist quoted in a New York Times article last year.

"If they're losing that much, then there is several times that area in various stages of deterioration. Losing it and abandoning it are sort of the final stage before it becomes desert," said Lester Brown, president of the Earth Policy Institute in Washington, D.C., which recently released an environmental alert on the problem.

Recurrent Problem

East-moving winds often carry soil away from China's northwest, where overplowing and overgrazing, coupled with periods of drought, has led to massive deterioration of the country's agricultural resources.

Huge dust plumes regularly travel hundreds of miles to Beijing and other cities in northeastern China. As they move over urban centers they pick up particles from industrial pollution.

The resulting dust clouds are often so thick they obscure the sun, reduce visibility, slow traffic, and close airports. Residents caulk windows with old rags to keep out the dust, and municipal crews have to clean public structures repeatedly during the dust-storm season.

The dust clouds are also a problem for China's neighbors, and North Korea, South Korea, and Japan have registered official complaints. Responding to pressure from their citizens, legislators from Japan and South Korea are organizing a tri-national committee with Chinese lawmakers to devise a strategy to combat the dust.

On March 10, 2001, The People's Daily reported that the season's first dust storm—one of the earliest on record—had hit Beijing. The recent dust storms and those of last year were said to be among the worst in memory.

(PhysOrg.com) -- The air we breathe doesn't always come from our own backyard. In fact, sometimes it doesn't even come from our neighbors.

On April 22, 2010, a NASA satellite captured the appearance of a large dust cloud over the eastern coast of United States that originated on the other side of the world -- in China.

"Dust can stimulate the production of more clouds, altering local weather and potentially the climate," said Zhoayan Liu, a researcher at the National Institute of Aerospace and NASA's Langley Research Center who is monitoring the dust movement. The dust cloud was in upper troposphere, the atmospheric layer in which we live.

The dust plume that arrived in the U.S. maintained an average size of more than 1,200 miles wide and six miles tall as it traveled across the Earth. It began in China's Taklimakan and Gobi Deserts, and over 10 days, NASA captured the dust moving across the Pacific Ocean, through the United States and Canada and over Virginia.

"It is likely that a cold front over the deserts generated strong surface winds that pushed a large amount of the dust into the atmosphere and from there the jet streams brought it across the world," said Liu.

Liu and his colleagues at NASA discovered the relocation of the dust after analyzing data from Langley's Earth observing satellite CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations). It can be difficult to distinguish dust from regular clouds and other types of aerosols in photographs taken from space. CALIPSO, however, measures vertical profiles of the atmosphere and produces data that makes a distinction between the different particle types in our atmosphere, such as clouds, smoke, or dust. Not only can it tell scientists what is in our air, CALIPSO can also identify the vertical and horizontal location of the particles as well.

To validate what the satellite saw, NASA scientists took to the sky with the NASA King Air B200 aircraft and a lidar instrument similar to the one on CALIPSO. Aboard the plane, scientists were able to take the same measurements as CALIPSO over North Carolina, Virginia, Maryland, Kentucky, and Pennsylvania. The local flights, which took place the same day and time that the satellite detected the dust, confirmed what the satellite observed.

"This transport of dust out of China happens every spring, but we rarely see it move this far with such intensity," said Raymond Rogers, a Langley scientist who participated in the local flights. The air is always made up of various kinds of particles, but it is uncommon that those particles relocate in such large amounts that can their origin can be visibly tracked.

Rogers and Liu said that using CALIPSO and local airborne measurements to monitor the presence of dust in our atmosphere will provide others with data that can be used to gain a better understanding of how dust impacts humans and ecosystems.